About 8:00am, a staffer went to tell the men that breakfast was ready. He noticed the door was ajar and discovered Mr Gumley lying on his bed with a blanket covering his head. He saw blood spatter on the wall and pulled the blanket down to discover a blue coloured strap around Mr Gumley's neck.

The police statement says Hindmarsh ran out of the room and later told staff he had "attacked Joe". Police allege Hindmarsh attacked Mr Gumley with his own guitar, causing fatal injuries to his face and head.

Ms Gumley told the ABC she could not understand why her son was placed in the same room as Hindmarsh, who had a history of violent offences.

"They've got a lot to answer for," Ms Gumley said.

"Why was that chap put in with him? Joe was never a fighter, he'd never fight."

Death not an isolated case

In January, the coastal town of Bulli was shocked when a man stabbed his sister to death and then stabbed himself.

The ABC has been told the accused, David Brown, and his sister, Therese Brown, were both patients at the Eloura West unit, however the local health district would not confirm this.

Police allege Brown stabbed his sister, who lived with him, multiple times before stabbing himself in the chest and driving 70 kilometres to Gladesville police station, where he turned himself in.

In April 2012, another former patient, who cannot be named for legal reasons, stabbed himself multiple times in the neck while suffering from psychosis.

And in August 2011, Suzie Onneeglio took a fatal overdose just weeks after being released from the Shellharbour mental health unit.

Her family said she was released to free up a bed in the ward.

Going further back to May 2005, 35-year-old Karen Keresztury died after her own battle with schizophrenia came to a shocking end.

Just weeks before she was released from Shellharbour Hospital, both Ms Keresztury's father and her 12-year-old daughter had pleaded with authorities to keep her in for further treatment.

Ms Keresztury left hospital and set herself on fire in front on her distraught child.

Nurses fear for their safety, union says

Some nurses at the unit say they have been assaulted at work and fear for their safety.

Brett Holmes from the NSW Nurses and Midwives Association told the ABC there had been problems at the unit for years.

"We have had incidents over the years in this unit and concerns from our membership about various issues, including assaults on our members by patients," Mr Holmes said.

"Our members are concerned that they are given proper management support and supervision, that they're provided with sufficient staff to look after the patients that are admitted to both the units.

"There is confusion about units being called high dependency yet not being recognised for that purpose when it comes to appropriate funding levels to sustain staffing that are needed when you have very close observation requirements of patients."

"Our members have been put under a great deal of scrutiny around this incident," he said.

"We think it's appropriate that there be a proper investigation and we're assisting our members to cooperate with that. But we would be very cautious should the investigations look like they're trying to look for scapegoats for what is a tragic situation."

Sue Browbank, chief executive of the Illawarra Shoalhaven Local Health District, said an internal investigation was underway, while the NSW Ministry of Health and NSW Police were also investigating the "tragic" incident.

"While the circumstances are being looked into as a matter of urgency, these investigations are extremely serious and must be comprehensive. This process can take time," she said.

"The matter is also currently before the court and the Local Health District, at this stage, is not in a position to make comment about specific details of the case or those involved as this may jeopardise or unduly influence the investigations.

She said the Eloura West Unit was an observation unit, not a high dependency facility.

"It caters for mostly involuntary patients who require observation, which is determined by the individual's acuity.

"Any reported incident of violence or assault at any hospital facility is taken very seriously and is always thoroughly investigated."

Anonymous email warned of attack

Lorraine Long from the Medical Error Action Group said she had received a number of complaints about the Eloura West unit.

The most recent, two weeks before the death of Mr Gumley, warned "someone shall be seriously attacked soon".

The email, which was sent anonymously, said: "There is a massive alcohol epidemic in Shellharbour and violence is a daily occurrence. The hospital has a Zero Tolerance Policy yet refuses to use the flagging/contract system of violent repeat offenders.

"Many staff have been assaulted, continuously there are incident reports, yet they always lead nowhere. Calls for 24/7 security fall on deaf ears. I believe someone shall be seriously attacked soon."

Ms Long said she had received similar emails about mental health care at Shellharbour Hospital over the years.

"It's staff contacting us," she said.

"They're concerned about safety for the staff, safety for the patients, security breaches, they're filling out incident reports, they're not being attended to.

"One of the things that worries me is why are staff from the Eloura mental health unit contacting the Medical Error Action Group to get something done? It indicates they're not being listened to by the Ministry of Health."

"It goes back years with the psychiatrist who left and another doctor who left and said 'I can't work here anymore'. We're not being listened to, [the] health department [is] not interested. But I think staff there are now worried for their personal safety and that is a concern."

Ms Long said nurses were forbidden from speaking publicly about their concerns under the terms of their employment contracts.